1. Field of the Invention
The present invention relates to a method of reducing the punching stress of a punching machine having a ram, in which punching machine a relative position of the punching tool upper part and the punching tool lower part is set by at least one mechanical or fixed abutment. The invention relates further to an apparatus for reducing the punching stress of a punching machine having a ram and at least one fixed abutment operative to set a relative position of the punching tool upper part and the punching tool lower part. At least one fixed abutment is mounted in the punching tool upper part and/or in the punching tool lower part, and the punching press includes a control means having an adjusting motor and is operative to adjust the height position of the ram during the working operation of the machine.
2. Description of the Prior Art
The height position of the ram specifically in case of high speed punching machines is a matter which must be given particular attention. An extremely precise lower dead point position of the ram within the entire range of operational speeds is, for instance, necessary if precise bends, embossments, cutting and scoring of tear-off covers are needed. If the lower dead point position is not maintained precisely, waste is produced. It is, furthermore, a desire to keep the immersing of the cutting dies of the punching tool upper part into the punching tool lower part at a minimal value such that during the resharpening of the tool as little material as possible must be ground away from the cutting plate. In case of a larger depth of immersion, more material must be removed from the stamp or die, and from the bottom die than in the case of a smaller depth of immersion. Accordingly, a tool must be resharpened less often until a complete replacing thereof is necessary.
Where more frequent resharpening of the tools is necessary quite obviously the number of parts produced by one given tool is less and correspondingly the production costs are higher.
In order to avoid such undesirable conditions it is a common procedure to provide fixed abutments at the punching tool lower part and the punching tool upper part. These fixed abutments maintain the relative end position of the punching tool upper part relative to the punching tool lower part constant over the entire speed range (i.e. number of strokes) of a given punching machine. However, the minimal necessary striking forces at a low number of strokes rise considerably with an increasing number of strokes and accordingly place quite a strain or stress, on a punching machine (see FIG. 3).